Erectile dysfunction is a disorder which is very common throughout the world. The recent introduction of sildenafil (the active ingredient in Viagra.RTM.) has improved the possibilities of treating this disorder significantly. Sildenafil and compounds closely related thereto are disclosed in EP 463 756, EP 702 555 and WO 98/49166 (all to Pfizer Ltd.).
However, despite the useful therapeutic properties of sildenafil, not all patients are successfully treated with this agent. Thus, there is still a great need in the art for compounds having improved therapeutic properties compared to sildenafil.